Say I have three settlements: A, B, and C
A has all my wood.
B has all my steel.
C has all my rubber.
Now if I set up a supply line from B to A and from C to A, A has access to all three. But does B or C have access to all three? Or do I need to also set up a supply line from B to C?
In other words, if you set up a supply line from Sanctuary to the Red Rocket Station, and one from the Red Rocket Station to the Starlight Drive-In, you can access the supplies from all three locations at all three locations.